Here are a few simple tips that I find keep my line limp and fishable:
1. Manually engage your bail with your hand, don't engage reel with the handle. This makes a world of difference, the action of the bail turning as it closes twists the line. Its not really any inconvenience once you are in the habit.
2. Buy good line and try to use choose a limper line, select XL instead of XT
3. When fishing soft plastics, keep your worms & craws as straight as possible on the hook, if you see your lure violently spinning as you reel your lure in for the next cast, that will cause your line to twist up and knot in no time.
4. When spooling up your reel, intermittently spray in some KVD line conditioner, this works great for me. You can find it at Bass Pro.
5. If your line is twisted, try running out your line behind the boat. As you are fast idling to your next fishing hole, let your line out with no lure or weight along the side of the boat. Let enough line for a couple long casts out and let it drag for 30-60 seconds. Reel it back in, it should be good as new!
6. If you want to use line heavier that 12lb on a spinning reel, use a braided line. I like to stick to 8 & 10lb lines on my spinning gear.
I hope you find this is helpful, if you have a tip of your own, leave a comment.